First published in 1914, as the second edition of a 1909 original, this book forms number ten in the Cambridge Tracts in Mathematics and Mathematical Physics series. It was written to provide readers with 'the main portions of the theory of integral equations in a readable and, at the same time, accurate form, following roughly the lines of historical development'. Textual notes are incorporated throughout. This book will be of value to anyone with an interest in integral equations and the history of mathematics.